No.
'66 and '67 short tail (A body) slant 6 and 273 four speeds had a 26 spline output shaft (same as a 904). Later in '67 when they introduced the big block 383 A bodies, they also introduced a larger output shaft with 30 splines (same as a 727). After that, they were all 30 spline starting in '68.
All long tail four speeds '65 and up were 30 splines from the get-go.
All '65 and earlier short tail four speeds and all '64 and earlier (I believe) long tail trannies had ball and trunnion output shafts.